A ginseng plant that is producing berries, has a decent root on it, and even if you topped it in early spring (after it first came up) it would not kill it (as in you would never see it again).
The root would develop a bud spur, and send up a top the next spring.
Deer top them all of the time, spring, summer, fall, and they normally come back the next spring. Occasionally they will lie dormant and not send up a top for a year or more, but then send up a top the next year.
I would think that you would do little if any harm to it if you topped it after berries were red.
Letting it run the full coarse naturally would definitely be best. Not sure if there are any studies out there on exactly how early you can top ginseng, without causing some degradation to the plant/root system.
No doubt if you topped it too early too often, the root would eventually give up and stop sending up a top. I expect that would take several years though. Ginseng is a SURVIVOR... and will fight to the very end.
I had a little 3 prong several years back that had the unfortunate luck to have two trees die just to the west of it (lightning strike). That let in the hot evening sun and was hard on the plant. I left it there for 3 years and observed what happend. The first year the top died in early June, the second year it died in late June, the 3rd year, it made it all the way to having a nice wad of green berries and then it died. I transplanted it after that.
In those 3 years, the open space that was made from the two trees that died, eventually was taken up by other trees that grew, or sent limbs into that space and filled it in. That is why it made it a little longer each year.
But even though it died early those 3 years, it still increased in size some and it went from not producing berries, to producing a nice little wad of berries.
Hope this helps.